To provide a DNA segment encoding each of recognition and cleavage domains of FokI restriction endonuclease.

The 41kDa N terminus fragment of FokI restriction endonuclease constitutes the recognition domain and the 41kDa C terminus fragment of the FokI restriction endonuclease constitutes the cleavage domain. As the hybrid restriction enzyme containing a nuclease domain of FokI restriction endonuclease connected with a recognition domain of another enzyme, Ubx-FN contains a Ubx homeodomain connected with the FokI cleavage or nuclease domain.